The invention concerns an implantable electrode arrangement which includes an electrode lead with a plurality of electrically conducting surface regions in the region of the distal end for outputting electrical signals to a heart and/or for receiving signals from a heart. The output and/or received signals can be connected by way of at least one electric line of the electrode lead to a cardioelectric device for a defibrillator or cardiac pacemaker where the cardioelectric where the cardioelectric device receives electrical signals and/or outputs pulses.
Electrode arrangements with an electrode line and a plurality of electrically conducting surface regions for example of tip or ring electrodes at the distal end of the electrode line are known for example from EP 0 571 797, U.S. Pat. No. 4,848,352 and U.S. Pat. No. 4,628,934. In the known electrode arrangements the electrically conducting surface portions which serve as stimulation or sensing electrodes are individually connected to a cardiac pacemaker or defibrillator by means of electric lines which extend in the electrode line. Each of the above-mentioned publications also describes selecting from the plurality of electrodes or electrode combinations, the respectively most suitable ones thereof in order to use them for example for stimulation of a human heart. A disadvantage with the known electrode arrangements is that they can usually only be employed together with specifically adapted cardiac pacemakers or defibrillators which make it possible at the proximal end of the electrode line to contact all feed lines which lead to the electrically conducting surface regions.
Conventional electrode arrangements are those in which only one or two electrical conductors extend in the electrode line, depending on whether the electrode arrangement is intended for unipolar or bipolar stimulation.
Electrode lines with a single-wire connection between the proximal end of the electrode line and the electrically conducting surface regions at the distal end of the electrode line are suitable for unipolar stimulation in which stimulation pulses are outputted between the electrically conducting surface regions at the distal end of the electrode line and a neutral electrode such as for example a casing of a cardiac pacemaker. Also known moreover is bipolar stimulation in which the stimulation energy is outputted between various ones of the electrically conducting surface regions at the distal end of the electrode line. For bipolar stimulation, the electrode line has a two-wire connection between the proximal and distal ends, such connection being made by way of two separate electric lines.
The object of the invention is to also make available the advantages of electrode arrangements having a plurality of electrically conducting and individually operable surface regions, for cardiac pacemakers or defibrillators having conventional one-wire or two-wire connections.
According to the invention that object is attained by an electrode arrangement of the kind set forth in the opening part of this specification, which is distinguished by switching means that are arranged in the electrode lead or line and are connected to the electric line and at least one electrically conducting surface region such that they can make or break a connection between the electrically conducting surface region and the cardioelectric device in the region of the electrode lead, and by control means that are arranged in the electrode lead and are connected to the electric line for receiving control signals and to the switching means for switching over from a state of the switching means of breaking the connection between the electric line and the electrically conducting surface region and a state of the switching means of making the connection and vice versa.
An electrode arrangement of that kind can conventionally be in the form of a single-wire or two-wire line with the usual electrical connections for a cardiac pacemaker or defibrillator. The control signals for the control means for switching the connection between individual electrically conducting surface regions and the cardiac pacemaker or defibrillator are put by the defibrillator, for example, in the form of digital signals onto the at least one electric line in the electrode lead and are thus passed to the control means. The control means decode each received control signal and correspondingly switch on or off individually or in groups connections between the electric line and the electrically conducting surface regions.
An electrode arrangement of that kind needs in the minimum situation only a single electrical conductor which goes from the proximal end of the electrode line to the switching means and the electrically conducting surface regions at the distal end of the electrode line. The reference potential for the control signals can then be produced for example by way of a neutral electrode with the casing of the pacemaker and can be available by way of the electrically conducting surface regions for the control means.
Preferably the switching means are of such a configuration and arrangement that, by way of the switching means, the connection can be made or broken individually or in groups between a plurality of and all electrically conducting surface regions and electric lines. That can be effected for example by a switching element being provided for each electrically conducting surface region. An electrode arrangement of that kind makes it possible to switch all possible combinations of electrodes.
Preferably, the control means are actuatable by control signals by way of the electric line in such a way that the connection can be made or broken individually or in groups between a plurality of or all electrically conducting surface regions and the electric line. For that purpose the control means include a decoder which for example can decode digital signals for switching the electrode connections on and off and can convert corresponding switching-on or switching-off signals for the switching means. For an electrode line with eight electrodes it is possible to use for example 8-bit control signals in which one bit is always precisely associated with an electrode and the value of the bitxe2x80x941 or 0xe2x80x94corresponds to the required switching state of the corresponding switching meansxe2x80x94on or offxe2x80x94. In this respect the digital control signals are so selected that they can be clearly identified, for example by virtue of their edge gradient, as control signals, even if they have superimposed thereon cardiac signals or voltage pulses for output to the heart. For that purpose the control means preferably have suitable filters which are so designed that they transmit only control signals to a decoder of the control means and retain further signals which are superimposed on the control signals.
In order to prevent damage to the control means for the stimulation pulses, there are preferably provided switch-off means which respond to stimulation pulses applied to the electric line and during the application of such pulses interrupt the connection between the control means and the electric line.
Preferably there is also provided an energy storage means which for the supply of energy for the switching and/or control means is connected thereto and can be charged up by way of the electric line. In that case the energy storage means is preferably a capacitor. The capacitor can be constantly charged with a low level of power by way of an electric one-wire or two-wire line of the electrode line and if required can also make available to the control or switching means higher levels of energy than is available by way of the electric line. In that case of a one-wire line the capacitor is charged by way of that one-wire line and one of the electrically conducting surface regions and a casing, which serves as a neutral electrode, of a cardiac pacemaker.
The switching means are preferably power field effect transistors. Practically no power is required for switching transistors of that kind. In addition in the conducting state such transistors have only a low level of ohmic resistance.
The control means preferably include electrically erasable or programmable read only memories, referred to as EEPROMs. In that way the control means can be easily programmed, that is to say it is easily possible to determine what kind of control signals produce which switching state in terms of the connection between the individual electrically conducting surface regions and the electrode line.
A cardiac pacemaker or defibrillator, for operation of an electrode arrangement of that kind, does not require any further components, apart from a signal generator for the control signals for the control means of the electrode arrangement. A signal generator of that kind preferably includes a storage means for preferred electrode combinations and the corresponding control signals.